1. Field of the Invention
The present invention relates to prosthetics and, more particularly, to foreshortened prosthetic legs (“Stubbies”) for bi-lateral above-the-knee amputation patients.
2. Description of the Background
There are a variety of different types of prosthetic devices for patients that have had either transfemoral (above-knee) or transtibial (below the knee) amputation. A typical modern prosthetic device consists of a custom socket fitted over the residual limb, a structural component system affixed to the socket that may include a pylon and articulated replacement joints (such as a knee or ankle) depending on the patient and location of the amputation, and knee cuffs, belts or other systems to secure the device to the body. A prosthetic sock or liner is typically worn over the residual limb within the socket to cushion the area of contact, and, in some cases, realistic-looking skin is provided over the structural components for aesthetic reasons.
One of the primary concerns of all prosthetic designs and construction is that the device be lightweight and provide a comfortable fit to the residual limb, and a natural gait when in use. This is an especially acute problem for bilateral above-knee amputees (BAKs). Because of the total loss of knee function most BAKs find prosthetic walking to be stressful and impracticable, especially the elderly. Indeed, very few BAKs can keep ambulatory control at all when using conventional bilateral leg prostheses. “Stubbies” are short prostheses comprising a standard socket, a leg with no articulated knee joints, and attached feet. Although stubbies are generally used as post-operative training devices to determine an amputee's ability to move to a standard, full-length prosthesis, they are also used for showering and other activities by amputees across the world.
Stubbies can include a variety of foot designs, ranging from standard prosthetic ankle/feet to rocker bottom platforms. If standard prosthetic feet are to be utilized, they are often set in a backwards position, with the heels facing the front. This is to help prevent the amputee from falling backwards. Rocker bottoms, although not realistic looking, offer greater anterior and posterior horizontal support. This increased ground level support provides an increased level of stability for the user. The typical rocker bottom foot design allows the bilateral leg amputee to achieve a lower center of gravity for better balance and stability. FIG. 1 is a perspective view of a pair of stubbies having prior art circular-platform feet.
Stubbies with rocker bottom feet are relatively easy to use, but are not conducive to ambulation because the platform feet typically cannot bend.
To provide the BAK amputee with a more comfortable and natural gait, it is of primary concern that a prosthetic foot be disposed at a suitable angle and orientation, be shaped appropriately, and flex properly relative to the direction of travel. These design criteria are not met by conventional stubby prostheses using rocker-bottom feet, and so it would be greatly advantageous to develop a stubby prosthetic with improved rocker bottom foot for improved ambulation.